refactor: Start making ledger helpers type-safe, beginning with AccountRoot

include/xrpl/ledger/View.h

@@ -18,6 +18,11 @@
 
 namespace xrpl {
 
+// Forward declarations for SLE wrappers
+template <typename ViewT>
+class AccountRoot;
+using RAccountRoot = AccountRoot<ReadView>;
+
 enum class SkipEntry : bool { No = false, Yes };
 
 //------------------------------------------------------------------------------
@@ -156,7 +161,7 @@ canWithdraw(
     ReadView const& view,
     AccountID const& from,
     AccountID const& to,
-    SLE::const_ref toSle,
+    RAccountRoot const& toWrapped,
     STAmount const& amount,
     bool hasDestinationTag);
 

include/xrpl/ledger/helpers/AccountRootHelpers.h

@@ -2,8 +2,10 @@
 
 #include <xrpl/basics/Expected.h>
 #include <xrpl/beast/utility/Journal.h>
+#include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/ReadView.h>
+#include <xrpl/ledger/helpers/SLEBase.h>
 #include <xrpl/protocol/Indexes.h>
 #include <xrpl/protocol/Rate.h>
 #include <xrpl/protocol/STLedgerEntry.h>
@@ -14,42 +16,160 @@
 
 namespace xrpl {
 
-/** Check if the issuer has the global freeze flag set.
-    @param issuer The account to check
-    @return true if the account has global freeze set
-*/
-[[nodiscard]] bool
-isGlobalFrozen(ReadView const& view, AccountID const& issuer);
-
-// Calculate liquid XRP balance for an account.
-// This function may be used to calculate the amount of XRP that
-// the holder is able to freely spend. It subtracts reserve requirements.
-//
-// ownerCountAdj adjusts the owner count in case the caller calculates
-// before ledger entries are added or removed. Positive to add, negative
-// to subtract.
-//
-// @param ownerCountAdj positive to add to count, negative to reduce count.
-[[nodiscard]] XRPAmount
-xrpLiquid(ReadView const& view, AccountID const& id, std::int32_t ownerCountAdj, beast::Journal j);
-
-/** Adjust the owner count up or down. */
-void
-adjustOwnerCount(ApplyView& view, SLE::ref sle, std::int32_t amount, beast::Journal j);
-
-/** Returns IOU issuer transfer fee as Rate. Rate specifies
- * the fee as fractions of 1 billion. For example, 1% transfer rate
- * is represented as 1,010,000,000.
- * @param issuer The IOU issuer
+/**
+ * View-parameterized wrapper for AccountRoot ledger entries.
+ *
+ * AccountRoot<ReadView>  — read-only access to account data
+ * AccountRoot<ApplyView> — read-write access, with insert/update/erase
+ *                          and domain-specific write methods
  */
-[[nodiscard]] Rate
-transferRate(ReadView const& view, AccountID const& issuer);
+template <typename ViewT>
+class AccountRoot : public SLEBase<ViewT>
+{
+    static constexpr bool kIsWritable = SLEBase<ViewT>::kIsWritable;
+
+    AccountID const id_;
+
+public:
+    /** Constructor for read-only context */
+    AccountRoot(
+        AccountID const& id,
+        ReadView const& view,
+        beast::Journal j = beast::Journal{beast::Journal::getNullSink()})
+        requires(!kIsWritable)
+        : SLEBase<ViewT>(view.read(keylet::account(id)), view, j), id_(id)
+    {
+    }
+
+    /** Constructor for writable context */
+    AccountRoot(
+        AccountID const& id,
+        ApplyView& view,
+        beast::Journal j = beast::Journal{beast::Journal::getNullSink()})
+        requires kIsWritable
+        : SLEBase<ViewT>(keylet::account(id), view, j), id_(id)
+    {
+    }
+
+    /** Converting constructor: writable → read-only. */
+    template <WritableView OtherViewT>
+    AccountRoot(AccountRoot<OtherViewT> const& other)
+        requires(!kIsWritable)
+        : SLEBase<ViewT>(other), id_(other.id())
+    {
+    }
+
+    /** Create an AccountRoot backed by a brand-new SLE.
+     */
+    [[nodiscard]] static AccountRoot
+    makeNew(
+        AccountID const& id,
+        ApplyView& view,
+        beast::Journal j = beast::Journal{beast::Journal::getNullSink()})
+        requires kIsWritable
+    {
+        return AccountRoot(id, view, j, std::make_shared<SLE>(keylet::account(id)));
+    }
+
+    [[nodiscard]] AccountID const&
+    id() const
+    {
+        return id_;
+    }
+
+    // --- Read-only domain methods (available on both specializations) ---
+
+    /** Check if the issuer has the global freeze flag set.
+        @return true if the account has global freeze set
+    */
+    [[nodiscard]] bool
+    isGlobalFrozen() const;
+
+    /** Returns IOU issuer transfer fee as Rate. Rate specifies
+     * the fee as fractions of 1 billion. For example, 1% transfer rate
+     * is represented as 1,010,000,000.
+     */
+    [[nodiscard]] Rate
+    transferRate() const;
+
+    // Calculate liquid XRP balance for an account.
+    // This function may be used to calculate the amount of XRP that
+    // the holder is able to freely spend. It subtracts reserve requirements.
+    //
+    // ownerCountAdj adjusts the owner count in case the caller calculates
+    // before ledger entries are added or removed. Positive to add, negative
+    // to subtract.
+    //
+    // @param ownerCountAdj positive to add to count, negative to reduce count.
+    [[nodiscard]] XRPAmount
+    xrpLiquid(std::int32_t ownerCountAdj) const;
+
+    /** Checks the destination and tag.
+
+       - Checks that the SLE is not null.
+       - If the SLE requires a destination tag, checks that there is a tag.
+    */
+    [[nodiscard]] TER
+    checkDestinationAndTag(bool hasDestinationTag) const;
+
+    /** Returns true if and only if sleAcct is a pseudo-account or specific
+        pseudo-accounts in pseudoFieldFilter.
+
+        Returns false if sleAcct is:
+        - NOT a pseudo-account OR
+        - NOT a ltACCOUNT_ROOT OR
+        - null pointer
+    */
+    [[nodiscard]] bool
+    isPseudoAccount(std::set<SField const*> const& pseudoFieldFilter = {}) const;
+
+    [[nodiscard]] bool
+    operator==(AccountRoot const& other) const
+    {
+        return id_ == other.id_;
+    }
+
+    [[nodiscard]] bool
+    operator==(AccountID const& other) const
+    {
+        return id_ == other;
+    }
+
+    // --- Write-only domain methods (compile-time gated) ---
+
+    /** Adjust the owner count up or down. */
+    void
+    adjustOwnerCount(std::int32_t amount)
+        requires kIsWritable;
+
+private:
+    // Private constructor only used by `makeNew`
+    AccountRoot(AccountID const& id, ApplyView& view, beast::Journal j, std::shared_ptr<SLE> sle)
+        requires kIsWritable
+        : SLEBase<ViewT>(std::move(sle), view, j), id_(id)
+    {
+        this->insert();
+    }
+};
+
+// CTAD deduction guide — bare AccountRoot(id, view) always deduces read-only.
+// For writable access, use WAccountRoot(id, applyView) explicitly.
+AccountRoot(AccountID const&, ReadView const&) -> AccountRoot<ReadView>;
+AccountRoot(AccountID const&, ReadView const&, beast::Journal) -> AccountRoot<ReadView>;
+
+// Backward-compatible aliases
+using RAccountRoot = AccountRoot<ReadView>;
+using WAccountRoot = AccountRoot<ApplyView>;
+
+// Explicit instantiation declarations (definitions in .cpp)
+extern template class AccountRoot<ReadView>;
+extern template class AccountRoot<ApplyView>;
 
 /** Generate a pseudo-account address from a pseudo owner key.
     @param pseudoOwnerKey The key to generate the address from
     @return The generated account ID
 */
-AccountID
+[[nodiscard]] AccountID
 pseudoAccountAddress(ReadView const& view, uint256 const& pseudoOwnerKey);
 
 /** Returns the list of fields that define an ACCOUNT_ROOT as a pseudo-account
@@ -62,27 +182,6 @@
 [[nodiscard]] std::vector<SField const*> const&
 getPseudoAccountFields();
 
-/** Returns true if and only if sleAcct is a pseudo-account or specific
-    pseudo-accounts in pseudoFieldFilter.
-
-    Returns false if sleAcct is:
-    - NOT a pseudo-account OR
-    - NOT a ltACCOUNT_ROOT OR
-    - null pointer
-*/
-[[nodiscard]] bool
-isPseudoAccount(SLE::const_pointer sleAcct, std::set<SField const*> const& pseudoFieldFilter = {});
-
-/** Convenience overload that reads the account from the view. */
-[[nodiscard]] inline bool
-isPseudoAccount(
-    ReadView const& view,
-    AccountID const& accountId,
-    std::set<SField const*> const& pseudoFieldFilter = {})
-{
-    return isPseudoAccount(view.read(keylet::account(accountId)), pseudoFieldFilter);
-}
-
 /**
  * Create pseudo-account, storing pseudoOwnerKey into ownerField.
  *
@@ -94,12 +193,4 @@
 [[nodiscard]] Expected<SLE::pointer, TER>
 createPseudoAccount(ApplyView& view, uint256 const& pseudoOwnerKey, SField const& ownerField);
 
-/** Checks the destination and tag.
-
-   - Checks that the SLE is not null.
-   - If the SLE requires a destination tag, checks that there is a tag.
-*/
-[[nodiscard]] TER
-checkDestinationAndTag(SLE::const_ref toSle, bool hasDestinationTag);
-
 }  // namespace xrpl

include/xrpl/ledger/helpers/CredentialHelpers.h

@@ -5,6 +5,7 @@
 #include <xrpl/beast/utility/Journal.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/ReadView.h>
+#include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/protocol/AccountID.h>
 #include <xrpl/protocol/STArray.h>
 #include <xrpl/protocol/STTx.h>
@@ -69,8 +70,7 @@ verifyDepositPreauth(
     STTx const& tx,
     ApplyView& view,
     AccountID const& src,
-    AccountID const& dst,
-    SLE::const_ref sleDst,
+    RAccountRoot const& dst,
     beast::Journal j);
 
 }  // namespace xrpl